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Author Topic:   The processes of evolution
Quetzal
Member (Idle past 5872 days)
Posts: 3228
Joined: 01-09-2002


Message 31 of 35 (19363)
10-09-2002 2:06 AM
Reply to: Message 27 by Itzpapalotl
10-08-2002 3:27 PM


Great links, Itz. Thanks [quetzal runs around immediately downloading the articles].

This message is a reply to:
 Message 27 by Itzpapalotl, posted 10-08-2002 3:27 PM Itzpapalotl has not replied

  
compmage
Member (Idle past 5153 days)
Posts: 601
From: South Africa
Joined: 08-04-2005


Message 32 of 35 (19379)
10-09-2002 8:31 AM
Reply to: Message 30 by Quetzal
10-09-2002 2:03 AM


So, if you get down to that level, there are no distinct species, right? Well, that just blew my arguement to bits. I thought the theory says that all live came from a single organism. I was going to argue genetic regresion, but seems like that one won't work so well anymore. Oh, well....
I thought of something else that is bothering me. Evolusion in an animals livestyle. Take that fish that swims upstream to mate where it was born. What's it called? Macerral? I think that's it, though I don't think that's the spelling. Anyway. Here you have a fish that mated in the oceans just like any other fish. Now it has to evolve the instinct to swim all the way back up a river. I don't think this can be caused by natural selection: The fish that just mate in the ocean where it is has a much better chance to pass on its genes than the fish that desides: "Mmmm I wonder what mating is like way up there". Chances are, he would not succeed. And even if it did, there must be at least two that was sucessful in their attempt before they can breed. The species as a whole needs to perfect this skill to swim all the way up a river, and it is more likely that none of those very early pioneers survived to pass on their genes.

This message is a reply to:
 Message 30 by Quetzal, posted 10-09-2002 2:03 AM Quetzal has replied

Replies to this message:
 Message 33 by Quetzal, posted 10-09-2002 10:33 AM compmage has replied

  
Quetzal
Member (Idle past 5872 days)
Posts: 3228
Joined: 01-09-2002


Message 33 of 35 (19395)
10-09-2002 10:33 AM
Reply to: Message 32 by compmage
10-09-2002 8:31 AM


quote:
Originally posted by Hanno:
So, if you get down to that level, there are no distinct species, right? Well, that just blew my arguement to bits. I thought the theory says that all live came from a single organism. I was going to argue genetic regresion, but seems like that one won't work so well anymore. Oh, well....
Well, you can separate bacteria into clonal lineages that are roughly equivalent to "species", based on actual genetic makeup, but we're getting a bit more technical here than your question required. For our purposes, there is no "hard and fast", reproductively isolated species like we mean when we talk about metazoan taxa.
quote:
I thought of something else that is bothering me. Evolusion in an animals livestyle. Take that fish that swims upstream to mate where it was born. What's it called? Macerral? I think that's it, though I don't think that's the spelling. Anyway. Here you have a fish that mated in the oceans just like any other fish. Now it has to evolve the instinct to swim all the way back up a river. I don't think this can be caused by natural selection: The fish that just mate in the ocean where it is has a much better chance to pass on its genes than the fish that desides: "Mmmm I wonder what mating is like way up there". Chances are, he would not succeed. And even if it did, there must be at least two that was sucessful in their attempt before they can breed. The species as a whole needs to perfect this skill to swim all the way up a river, and it is more likely that none of those very early pioneers survived to pass on their genes.
Actually, it isn't that hard (sorry, again - eventually you WILL ask a question I haven't already researched somewhere ). The question really departs a bit from evolution, and lands in the area of behavioral ecology. One thing to realize is that although the pathways are different, the selection pressures that lead to the evolution of migration in fish are really no different from those that lead to migration in birds, sea turtles, etc. IOW, food supply, predation pressure, climate, etc. The specifics will vary depending on whatever organism you’re dealing with. Moreover, not all members of a particular fish species — or even population — will necessarily migrate. I don’t know about mackerel, but this is certainly true of many species of salmon, for instance (see jack salmon, which grow to full size in their native river while the rest of their population does full migration). Anyway, the idea is that there is selection pressure related to higher productivity in oceans than in rivers, hence the adaptive advantage of migration. It’s interesting to note that the reverse is true in the tropics, where rivers have higher productivity — some marine species grow to adulthood in the rivers, but breed in either saline estuary or even the open ocean. (search for anadromy and catadromy for examples). We can still see this in action — coho salmon were introduced into New Zealand, and soon diversified (primarily due to the genetic plasticity of this species) into both anadromous and catadromous populations — with some being extremely lazy and adapting to a purely lake- or river-dwelling lifestyle - all in only ten years. Given the number of salmon populations that are known to thrive even cut off from the ocean, this adaptability doesn't really surprise me.
Here are a couple of articles: Evolution of Diadromy in Fishes and Evolution of Life History and Migration in Fish

This message is a reply to:
 Message 32 by compmage, posted 10-09-2002 8:31 AM compmage has replied

Replies to this message:
 Message 34 by compmage, posted 10-09-2002 11:59 AM Quetzal has not replied

  
compmage
Member (Idle past 5153 days)
Posts: 601
From: South Africa
Joined: 08-04-2005


Message 34 of 35 (19420)
10-09-2002 11:59 AM
Reply to: Message 33 by Quetzal
10-09-2002 10:33 AM


Thanks.
I can't think of anything else right now, but I'm sure it's just a matter of time before my creationist mind think up something else again.
Cheers.

This message is a reply to:
 Message 33 by Quetzal, posted 10-09-2002 10:33 AM Quetzal has not replied

Replies to this message:
 Message 35 by nos482, posted 10-09-2002 12:26 PM compmage has not replied

  
nos482
Inactive Member


Message 35 of 35 (19424)
10-09-2002 12:26 PM
Reply to: Message 34 by compmage
10-09-2002 11:59 AM


quote:
Originally posted by Hanno:
Thanks.
I can't think of anything else right now, but I'm sure it's just a matter of time before my creationist mind think up something else again.
Cheers.

Ain't an imagination a wonderful thing?

This message is a reply to:
 Message 34 by compmage, posted 10-09-2002 11:59 AM compmage has not replied

  
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